As temperature of semiconductor light emitting elements becomes higher, luminous efficiency of the elements decreases, and higher temperature more shortens lifetime of the elements. Therefore, it is desired to increase heat radiation efficiency of semiconductor light emitting elements. For example, Patent document 1 discloses a structure that a metal body for heat radiation is adhered to a lead to be connected to a bottom surface electrode of a semiconductor light emitting element with a thin insulating adhesive layer so that heat of the semiconductor light emitting element is efficiently conducted to the metal body via the thin insulating adhesive layer.
Patent document 2 discloses an LED package carrying an LED chip so that the chip should directly contact with a metal-impregnated carbon material. The metal-impregnated carbon material is prepared by sintering hardened carbon powder or carbon fibers and impregnating the sintered body with a metal such as Cu or Al, and shows high thermal conductivity.
Patent document 3 discloses a configuration that a semiconductor light emitting element is carried on a substrate consisting of an anisotropic heat conduction layer showing larger thermal conductivity for the plane direction compared with thermal conductivity for the thickness direction, and isotropic heat conduction layers on the both surfaces of the anisotropic heat conduction layer. This aims at diffusing heat along the plane direction by using the anisotropic heat conduction layer. As the anisotropic heat conduction layer, graphite is used.
Patent document 4 discloses a configuration that an LED chip is carried on a metal heat sink, and a pattern wiring, an insulating layer, a metal core printed circuit board, and a body are disposed in this order under the heat sink. For the body, graphite showing anisotropic thermal conductivity is used to increase conduction of heat of the LED chip along the plane direction.
Patent document 5 discloses a configuration that a fluorescent substance layer for color conversion is disposed on an LED chip, wherein a metal mesh or wire rod for heat radiation is disposed inside the fluorescent substance layer. By this configuration, heat in the fluorescent substance layer is conducted with the metal mesh or the like to a base (ring) surrounding the fluorescent substance layer and thereby prevent decrease in quantity of light due to rise in temperature of the fluorescent substance.